The present invention is related to an image scanning device, and more particular to an image scanning device having an image data correction function for improving image quality and uniformity. The present invention also relates to a method for correcting image data of a scanned object.
In general, an image scanning device picks up the image data of a scanned object though the following path. Light is emitted from a light source to the scanned object which reflects light therefrom or allows light to pass therethrough to a mirror set. The mirror set further reflects light to a lens set to be focused, and then the focused light is transmitted to a photoelectric converter such as a charge coupled device (CCD) for further processing. Owing to a long journey of the light from the light source to the photoelectric converter and a long journey of the above mentioned scanning devices from the start to the end during a scanning process, various errors may occur. In general, errors may result from the poor coordination among the cells in the photoelectric converter and the light source, and the cos4xcex8 effect of the lens set. These errors can be compensated by performing a standard scanning process prior to a formal scanning process for calibration. In addition, errors may also be caused by the noises generated by the photoelectric converter, and so far, there is no way to compensate such an error unless the manufacturer of the photoelectric converter develops an improved device. Moreover, a source of error up to about 3%xcx9c5% is the uneven light emission of the light source at different time points. There has been no scanning device manufacturer taking action to compensate such an error yet.
An object of the present invention is to provide an image scanning device which is capable of compensating an error resulting from uneven light emission of the light source at different time points by the installation of a photo-detector.
Another object of the present invention is to provide a method for correcting image data of a scanned object, which provides optical data of the light source at different time points as references to correct the image data of the scanned object.
According to a first aspect of the present invention, an image scanning device for realizing image data of a scanned object includes a light source for providing a source light for the scanned object in order to obtain an optical image signal; a photo-detector for detecting and recording a scanning light intensity of the source light; and optical signal processing means for receiving and converting the optical image signal into an electronic image signal, the optical signal processing means being electrically connected to the photo-detector for reading the scanning light intensity of the source light, and adjusting the electronic image signal according to the scanning light intensity of the source light so as to realize the image data of the scanned object.
In a preferred embodiment, the optical signal processing means includes a photoelectric converter, e.g. a charge coupled device (CCD), for receiving and converting the optical image signal into the electronic image signal; and an operational processor electrically connected to the photoelectric converter and the photo-detector for reading the scanning light intensity and a reference light intensity which are recorded by the photo-detector at a scanning position and a reference position, respectively, and adjusting the electronic image signal according to the scanning light intensity and the reference light intensity. In this preferred embodiment, the operational processor adjusts voltage values of the electronic image signal according to a ratio of the scanning light intensity to the reference light intensity.
Preferably, the operational processor includes a divider electrically connected to the photo-detector for reading the scanning light intensity and the reference light intensity from the photo-detector to obtain the ratio; and a multiplier electrically connected to the divider and the photoelectric converter for adjusting the electronic image signal by multiplying the voltage values of the electronic image signal by the ratio, and more preferably, further includes a correction circuit electrically connected to the operational processor for correcting the adjusted electronic image signal according to voltage values of a standard measured at the beginning of a scanning process so as to precisely realize the image data of the scanned object.
If the system is operated digitally, the optical signal processing means should further include an analog/digital converter electrically connected to the photoelectric converter and the operational processor for converting voltage values of the electronic image signal into digital voltage values.
Generally, voltage values of the electronic image signal include respective voltage values of a red, a green and a blue colors in the electronic image signal.
If the image scanning device according to the present invention is a reflection type of scanner, the light source, the photo-detector, and the optical signal processing means are contained in a carriage to be moved together along a guiding track.
If the image scanning device according to the present invention is a transmission type of scanner, then the light source and the photo-detector are located on a side of the scanned object opposite to the optical signal processing means.
In accordance with a second aspect of the present invention, a method for adjusting scanned image data of an object according to the light intensity of a source light provided for the object during scanning, includes steps of: recording a reference light intensity of the source light detected at a reference position; recording a scanning light intensity of the source light detected at a scanning position; obtaining a calibration value according to the reference light intensity and the scanning light intensity; and adjusting the scanned image data of the object by an arithmetic operation between the scanned image data and the calibration value.
The scanned image data generally include voltage values of a red, a green and a blue colors.
According to a preferred embodiment of the present invention, the step c) of the method is executed on the basis of the formulae of d=A/B, in which
d indicates the calibration value,
A indicates the reference light intensity, and
B indicates the scanning light intensity.
Furthermore, the step d) can be executed on the basis of the formulae of
RB=RBxe2x80x2xc3x97d
xe2x80x83GB=GBxe2x80x2xc3x97d
BB=BBxe2x80x2xc3x97d
in which:
RB, GB and BB indicate voltage values of a red, a green and a blue colors of the adjusted image data after the step d), respectively; and
RBxe2x80x2, GBxe2x80x2 and BBxe2x80x2 indicate voltage values of a red, a green and a blue colors of the scanned image data, respectively.
If the color effects of respective red, green and blue colors are to be further independently adjusted in addition to compensation, then a step e) of adjusting the scanned image data according to three parameters corresponding to color effects of a red, a green and a blue colors, respectively, can be executed.
The steps d) and e) can be executed on the basis of the formulae of
RB=RBxe2x80x2xc3x97dxc3x97CR
GB=GBxe2x80x2xc3x97dxc3x97CG
BB=BBxe2x80x2xc3x97dxc3x97CB
in which:
RB, GB and BB indicate voltage values of a red, a green and a blue colors of the adjusted image data after the steps d) and e), respectively;
RBxe2x80x2, GBxe2x80x2 and BBxe2x80x2 indicate voltage values of a red, a green and a blue colors of the scanned image data, respectively; and
CR, CG and CB indicate coefficients for further independently adjusting voltage values of a red, a green and a blue colors of the scanned image data, respectively.
Preferably, the method further includes steps of recording voltage values of a red, a green and a blue colors of a standard object, and correcting the voltage values of the adjusted image data after the step d) according to the voltage values of the standard object. This correction step, although not an essential step of the present invention, can further improve the image compensation effect of a scanned document. Such a correction step has been popularly used in the scanner field, and is well known to those skilled in the art, so it will not be redundantly described here.